How to deter Field Mice?

Last year I was left with virtually nothing thanks to a few little field mice. What's the best way to deter these critters?

C4? - kidding. Actually not kidding.

I noticed a new hole last week in the middle of my cleared ground bed that I was planning on putting my roots in this year. And there was a little field mouse sitting next to it, bold as brass, out in the sunlight.